1. Field of the Invention
The present invention relates to a locking device of a paper feed tray and an image forming apparatus, and, more particularly to a locking device of a paper feed tray including an engaging member arranged in one paper feed tray and a to-be-engaged member arranged in the other paper feed tray, of paper feed trays arranged in parallel at storage positions of an image forming apparatus, and to an image forming apparatus including the locking device. The locking device can set to an interlocked state where the engaging member and the to-be-engaged member are in an engageable state and both of the paper feed trays are coupled to transmit a drawing force of the one paper feed tray to the other paper feed tray so that both of the paper feed trays can be drawn out together, and to a separated state where the engaging member and the to-be-engaged member are not engaged with each other, and the paper feed trays are separated from each other so that each paper feed tray can be drawn out individually.
2. Description of the Related Art
Some paper feeding apparatuses used in a copying machine and the like include a paper feed tray referred to as a tandem tray to which two paper feed trays are positioned in parallel. In the paper feeding apparatus including such a tandem tray, if a paper feed tray on a paper feed unit side is designated as a first paper feed tray, and the other paper feed tray is designated as a second paper feed tray, sometimes a locking device is provided. With the locking device, the paper feed trays can be coupled to or de-couples from each other according to circumstances. In this configuration, when the first and second paper feed trays are not feeding sheets, by coupling the first and second paper feed trays together with the locking device, both the feed trays can be drawn out together. On the other hand, when the first paper feed tray is feeding sheets, by de-coupling the first and second paper feed trays by releasing the locking device, only the second paper feed tray can be drawn out. A paper feed tray is drawn out from the paper feeding apparatus when replenishing sheets.
Japanese Patent No. 2831458 discloses an image forming apparatus in which each paper feed tray of a so-called tandem tray including a first paper storage unit (a first paper feed tray) and a second paper storage unit (a second paper feed tray) is formed of an independent tray member, a guide rail is installed so that these paper feed trays are drawn out at a substantially right angle to a sheet transport direction (forward of the machine), and a locking mechanism that couples and integrates the first and second paper feed trays is provided so that when the locking mechanism is operated, if one paper feed tray is drawn out, the other paper feed tray can be drawn out together.
The image forming apparatus disclosed in Japanese Patent No. 2831458 is explained below. FIG. 7 is a sectional view of an image forming apparatus 1 (copying machine) with a tandem tray incorporated therein. In the image forming apparatus 1, a manuscript is set on a contact glass 10, a surface of the manuscript is irradiated with light generated by a light source 9, light reflected from the manuscript is directed to a photoconductor 12 by an optical system 11 thereby forming a latent image on the photoconductor 12. The latent image on the photoconductor 12 is developed by a developing device 14 into a visual image. The visual image on the photoconductor 12 is transferred onto a printing paper P in a transfer and separation unit 15 and fixed to the printing paper P by a fixing device 17. In FIG. 7, reference numeral 13 denotes a charger that charges the photoconductor 12, 16 denotes a cleaning apparatus that removes residual toner on the photoconductor 12, 18 denotes a pair of registration rollers that performs positioning of printing paper, 19 denotes a large paper feed tray that stores large printing paper, and 20 and 21 denote first and second paper feed trays, respectively. The first and second paper feed trays 20 and 21 form the tandem tray. The first and second paper feed trays 20 and 21 store printing paper P1 and P2, respectively. Further, reference numeral 22 denotes a printing-paper feed path, 23 denotes a manual paper feed unit, and reference characters L1, L2, L3, L4, and L5 denote guide rails, and reference characters P1 and P2 denote printing paper.
A configuration of a paper feed unit of the image forming apparatus 1 is explained next. In the paper feed unit, a shift mechanism that shifts the printing paper from the one paper feed tray to the other paper feed tray is provided in the paper feed unit in addition to a locking mechanism. FIG. 8 is a plan view of an entire configuration of the paper feed unit at the time of storing the paper feed trays in the image forming apparatus shown in FIG. 7. FIG. 9 is a front view of the transfer paper storage unit shown in FIG. 8. FIGS. 10A and 10B depict a state of the locking mechanism at the time of storage in a conventional image forming apparatus, where FIG. 10A is a schematic diagram of a coupled state and FIG. 10B is a schematic diagram of an operation to shift from a released state to the coupled state. FIGS. 11A and 11B depict a movement of the two paper feed trays in the conventional image forming apparatus, where FIG. 11A is a plan view of a state where coupling is released and one of the paper feed trays is drawn out, and FIG. 11B is a plan view of a state where the two paper feed trays are drawn out in the coupled state.
In FIGS. 8 and 9, reference numeral 25 denotes a transfer path provided between the first paper feed tray 20 and the second paper feed tray 21 for transferring the transfer paper P2 from the second paper feed tray 21 to the first paper feed tray 20. Reference numeral 27 denotes a handle provided in the second paper feed tray 21, 34 and 35 denote a pair of side fences, 36 denotes a back fence, 37 denotes a rotatable bottom plate (capable of rising) with one end 37b engaging with the first paper feed tray 20, 38 denotes a solenoid for evacuating the back fence 36 from the transfer path 25, 39 denotes a rising unit that drives the bottom plate 37, and 40 denotes a bottom plate adhered to the second paper feed tray 21. Reference numeral 41 denotes a movable back fence, which is a transfer unit that transfers the transfer paper P2 to the first paper feed tray 20 collectively by pressing substantially a central part of a rear end of the transfer paper P2 stacked on the bottom plate 40. Reference numeral 42 denotes a hole formed in the bottom plate 40 so that a pressing unit 41a of the movable back fence 41 can move, and 43 denotes a wire coupled with a coupling unit 41b at a bottom end of the pressing unit 41a. Reference numerals 44 to 47 denote a pulley that stretches the wire 43 in a tense state, and 48 denotes a reversible motor that rotates the pulley 45 forward and backward. Reference numeral 49 denotes a home position sensor and 50 denotes a positioning sensor, which detect the movement of a protruding portion 41c of the movable back fence 41. Reference numeral 51 denotes a paper-bundle detection sensor that detects presence of the transfer paper P2 on the bottom plate 40. Further, reference numeral 52 denotes a pressing plate with one end thereof passes through a hole 20a in the paper feed tray 20 to abut against the bottom plate 37, 53 denotes a pressurizing shaft that supports the other end of the pressing plate 52, and 54 denotes a reversible motor that drives a sector gear 53a provided at a shaft end of the pressurizing shaft 53. Further, reference numeral 60 denotes a locking mechanism that sets to a locked state where the first and second paper feed trays 20 and 21 are coupled with each other or an unlocked state where engagement of both of the paper feed trays is released, 61 denotes a lock-releasing solenoid, 62 denotes an engagement claw member, 63 denotes a shaft of the engagement claw member, 64 denotes a torsion spring, 65 denotes a plunger of the solenoid, 66 denotes a release lever, 67 denotes a return spring, and 68 denotes a support hole for the engagement claw member.
In such an apparatus, when the locking mechanism 60 is set to the locked state, as shown in FIGS. 10A and 11A, the engagement claw member 62 engages with the support hole 68, to couple the first and second paper feed trays 20 and 21 with each other. By pulling the handle 27 of the second paper feed tray 21, the paper feed trays 20 and 21 can be drawn out.
On the other hand, when the locking mechanism 60 is set to the unlocked state, as shown in FIGS. 10B and 11B, in a state where the engagement claw member is released (in a portion indicated by a dotted line), when the handle 27 of the second paper feed tray 21 is pulled, only the second paper feed tray 21 is drawn out. From this state, when the second paper feed tray 21 is to be stored, the engagement claw member moves in a counter-clockwise direction as shown in FIG. 10B, and when reaching a coupling position, the engagement claw member is fitted into the support hole due to a spring force, so that the two paper feed trays become a coupled state.
In the image forming apparatus 1, a paper-feed-tray pushing device is provided for pushing out the paper feed tray to the outside when the locking mechanism that positions and fixes the paper feed tray in the image forming apparatus is released. FIGS. 12A and 12B depict the paper-feed-tray pushing device, where FIG. 12A is a schematic diagram of a state where the paper feed tray is stored, and FIG. 12B is a schematic diagram of a state where the paper feed tray is pushed out. In this example, the pushing device includes a paper-feed-tray locking device 80 that fixes the paper feed tray 20, and a compression spring 90 that pushes out the paper feed tray 20.
The paper-feed-tray locking device 80 can operate the paper feed tray to a locked state where movement of the paper feed tray 20 toward a near side (to the right in FIGS. 12A and 12B) is restricted or to an unlocked state where the movement of the paper feed tray 20 toward the near side is allowed, and is provided at an end on the near side of the paper feed tray 20. The paper-feed-tray locking device 80 is constituted by arranging an arm member 81 rotatably around a rotation shaft 83, which includes, at one end thereof, an engagement claw 82 that engages with a protrusion 71 of an image forming apparatus body 70 to restrict the paper feed tray 20 from being drawn out, and at the other end, a handle 84 for operating the paper-feed-tray locking device 80. The paper-feed-tray locking device 80 becomes the locked state by pushing in the paper feed tray 20 and engaging the engagement claw 82 with the protrusion 71, or the unlocked state by operating the handle 84 to rotate the arm member 81 to thereby release the engagement between the engagement claw 82 and the protrusion 71.
The compression spring 90 is compressed due to insertion of the paper feed tray 20, to energize the paper feed tray 20 toward the near side. As shown in FIG. 12A, therefore, in a state where the paper feed tray 20 is inserted into the image forming apparatus body 70, a force toward the near side is applied to the paper feed tray 20 due to the compression spring 90, and the engagement claw 82 engages with the protrusion 71 to hold an arrangement position of the paper feed tray 20.
When the paper feed tray is to be drawn out, the handle 84 is operated to rotate the arm member 81, to thereby remove the engagement claw 82 from the protrusion 71. Due to this operation, the paper feed tray 20 moves toward the near side due to an energizing force of the compression spring 90.
Thus, a user performs only one operation of operating the handle 84. Mechanically, however, two operations of releasing the lock of the paper-feed-tray locking device 80 and drawing out the paper feed tray 20 are performed, and because actions of forces thereof are different, an operating force changes along the way. Therefore, there is such a problem that if the handle is operated with a stronger force because the operating force is large, the necessary operating force decreases abruptly and the paper feed tray may spring out swiftly, or if the handle is operated with a weaker force because the operating force is small, the necessary operating force increases abruptly and user's hand may come off the handle. Under such circumstances, the user may have a feeling of danger.
FIGS. 13A to 13D depict another example paper-feed-tray pushing device, where FIG. 13A is a schematic diagram of a stored state of the paper feed tray, FIG. 13B depicts a state of the force in the stored state, FIG. 13C is a schematic diagram of a pushed state of the paper feed tray, and FIG. 13D depicts a state of the force in the pushed state. In the pushing device according to this example, a slope member 120 is arranged at an end of the paper feed tray 20 on a back side thereof, and the slope member 120 is pressed by a pressing member 130 to energize the paper feed tray 20 to the back side or the near side. Further, a handle 110 is arranged on the near side of the paper feed tray 20, and a stopper 72 that restricts movement of the paper feed tray 20 toward the back is formed on the back side of the image forming apparatus body 70. The slope member 120 includes two slopes 121 and 123 having different inclinations arranged at an end of a connecting part 124 protruding from the paper feed tray 20 toward the back, putting a ridge 122 therebetween.
Further, in the pressing member 130, a roller member 131 that comes in contact with the slopes 121 and 123 of the slope member 120 is positioned at an end of an arm member 132 rotatably held to the image forming apparatus body 70 by a rotation shaft 133, to thereby energize the arm member 132 by a tension spring 134. In the pushing device having such a configuration, a downward force F acts on the roller member 131, and at a point of contact with the slope 121, the downward force F acts on the slope 121, and an extrusion force F4 acts on the paper feed tray 20 (see FIGS. 13B and 13D). A size of the extrusion force F4 is mainly determined by gradients of the slopes 121 and 123, and the extrusion force F4 becomes a main force to move the paper feed tray 20 horizontally.
As shown in FIGS. 13A and 13B, in the stored state, a backward extrusion force F4 acts on the paper feed tray 20, and the paper feed tray 20 bumps against the stopper 72 and is positioned. On the other hand, when the paper feed tray 20 is drawn out by the handle 110 against the backward force, the roller member 131 ascends the slope 121, and when the roller member 131 passes the ridge 122, the roller member 131 comes in contact with a downhill slope 123, and a forward extrusion force F4 acts on the paper feed tray 20.
Also in this example, because the force acting on the paper feed tray 20 is different for each of a state where the roller member 131 ascends the slope 121, a state where the roller member 131 descends the slope 123, and a state where the roller member 131 comes off the slope 121, the user feels the difference as a change of the operating force.
As described above, there is a problem that user's operational feeling is not good due to a change of the operating force, at the time of drawing out the paper feed tray positioned and arranged in the image forming apparatus. Particularly, as in the tandem tray, when a plurality of paper feed trays are arranged, two different operations of releasing the locking device and thereafter drawing out the paper feed tray are required for drawing out the stored paper feed tray. Therefore, an impact accompanying the movement of the paper feed tray and a change of the operating force cannot be avoided during one operation performed by the user such as pulling the handle. When right and left two trays of the tandem tray are to be drawn out simultaneously, the impact and the change of the operating force are accumulated, and thus the unpleasant feeling caused on the user can be increased.